The invention relates to a valve actuation mechanism for an internal combustion engine with three inlet valves per cylinder which are actuated by cams of a camshaft by way of rocker arms.
In a known valve actuation mechanism of this type (e.g. DE-A 38 00 347), two first rocker arms are provided for actuating two inlet valves, which rocker arms interact with identical first cams so that in the first (lower) rotational speed range, all the inlet valves are actuated in an identical manner. Two second rocker arms are arranged between the first rocker arms or outside the same and these second rocker arms interact with different second cams. In one embodiment, each second rocker arm can be coupled to the adjacent first rocker arm. In another embodiment, the first rocker arms are connected together by a bridge and one or the other second rocker arm can be optionally coupled to the bridge and, by this means, to the two first rocker arms. For the actuation of three inlet valves, two first rocker arms interacting with identical cams are provided in a manner analogous to the second embodiment. These rocker arms are connected together by a bridge which acts on the three inlet valves. The two second rocker arms, which are arranged adjacent to one another and between the two first rocker arms, can be optionally coupled to the bridge and, by this means, to the two first rocker arms. In these known embodiments, the opening force exerted by the second cams in the coupled condition acts to one side of the first rocker arms or asymmetrically on the bridge connecting the first rocker arms together so that a tipping moment is generated which makes the decoupling, in particular, more difficult and, in the extreme case, can lead to jamming of the coupling means.
JP-A-60-216014 describes a valve actuation mechanism for an internal combustion engine with three inlet valves per cylinder which are actuated via rocker arms by cams of a camshaft. In this publication, each valve has its own rocker arm associated with it, which rocker arm is supported on its own rocker arm support and interacts with its own cam. No second rocker arms are provided to connect for valve control as a function of rotational speed, to the three rocker levers by coupling means.